Improving the performance of horizontal directional drill pipes primarily involves optimizing the design of pipe specifications and dimensions, using high-strength steel materials, enhancing end connection structures and thread types, improving manufacturing processes, and implementing proper field usage and maintenance.
(1) Adopting Appropriate Specifications and Dimensions
The drill pipe diameter should match the borehole diameter and axial load. Wall thickness should consider both strength and ease of operation. Pipe length should be flexible, taking into account workspace, drilling rig specifications, and borehole length.
(2) Using High-Quality, High-Strength Steel Materials
Drilling pipe strength is typically expressed in terms of yield strength, using standards from oil exploration and mineral core drilling. Historically, Grade E steel pipes were used extensively, but the industry has gradually progressed to X95, G105, S135, U170, etc., utilizing high-quality alloy steels with heat treatment (quenching and tempering).
(3) Employing Internal Thickening or Welded Joints at Pipe Ends
To increase the effective cross-sectional area of the threaded portion, making its strength consistent with or even exceeding that of the pipe body, the oil exploration industry once proposed that the torsional strength of joints should be 13%-20% greater than that of the pipe body as a safety factor. The thickness of drill pipe joints must be significantly greater than the pipe body thickness to accommodate thread machining, and various thickening and welding methods can be employed.
(4) Selecting Appropriate Thread Types
This includes thread type, helix angle, taper, sealing shoulder, stress relief groove, and manufacturing inspection. The threaded portion is the most critical area for stress concentration and wear on drilling pipes. In addition to increasing wall thickness, the design and manufacturing of the threads themselves directly affect its performance.
(5) Proper Operation and Maintenance
Proper operation and maintenance can extend the service life and prevent accidents.
① Ensure that the specifications and performance (diameter, wall thickness, and steel grade) match the various loads encountered during operation.
② Carefully consider the borehole diameter, trajectory design, and drill pipe load capacity during construction. Strive for designs with small entry and exit angles, large radii of curvature, and fewer bends. For shallow pipelines, adopt working pit designs where appropriate to reduce curved sections. These measures help reduce overall stress and wear on drilling pipes, particularly ensuring that torsional stress remains within safe limits to prevent pipe failure.
③ Apply appropriate torque when connecting pipes. Prevent over-tightening or under-tightening, and strictly avoid damage from chuck jaws and pipe tongs.
④ Advanced drilling rigs have automatic feed, lifting, moving, centering, make-up and break-out, and thread compound application mechanisms. They display real-time parameters such as torque, rotation speed, and axial load, with warning systems to prevent overload operations, helping to protect them.
⑤ Use high-quality thread compound containing soft metal materials.
⑥ Regularly inspect for integrity and wear.
⑦ For temporarily unused pipes, thoroughly clean the exterior, interior, and threaded portions, apply specialized anti-rust oil, use thread protectors, and store properly.
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